This invention relates to a sensor for detecting changes in the critical parameters affecting superconductors, and to a method and apparatus therefore.
It is known that superconductors are constrained to operate within specific limits identified as the Critical Current as well as the Critical Temperature and the Critical Magnetic Field. If the strength of the magnetic field surrounding a current-carrying superconductor is allowed to exceed the critical value, the conductor will abruptly lose its superconducting ability and will revert to the normal current-carrying mode for its specific material. If the surrounding temperature is allowed to increase above the critical value, a superconductor similarly may lose its superconducting ability, abruptly.
Because superconductors for power transmission applications may carry extremely high electrical currents (on the order of 10,000 amperes) in routine operation, a sudden loss of superconducting ability can cause serious physical damage to the superconductor itself and surrounding structures, if the overall conductor structure is unable to carry the full current under non-super conducting conditions. The principal design feature of a superconductor is the carrying of high levels of current. Many composite superconductor structures of modern design include some provision for shunting the high operating currents which they carry in normal operation, through an integrally formed non-superconducting structure, when superconductivity is lost temporarily. This "shunting" mode of operation provides desirable protection for the superconductor structure and its associated structures and circuits; however, the preservation of substantially uninterrupted current flow in this manner, may mask or suppress current flow variations which would otherwise provide meaningful warning signals of abnormal or undesirable conditions in the critical parameters.
For these reasons it is desirable to detect changes in the critical parameters of temperature and magnetic field strength in the immediate environment of a superconductor, as soon as possible, and to anticipate changes in these parameters which may lead to the loss of superconductivity.
Accordingly, it is an object of this invention to provide a sensor capable of functioning in the normal operating environment of a superconductor cable.
It is a further object of this invention to provide a sensor conductor structure embodying superconductive material which is particularly adapted for use in close proximity to a current-carrying superconductor to detect changes in the ambient critical parameters.
Still another object of this invention is to provide an assembly having means for generating signals indicative of changes in the critical parameters in the immediate environment of a superconductor.
And, still another object of this invention is to provide an assembly of the type described which is capable of providing signals indicative of changes in the temperature and the magnetic field surrounding a superconductor before the superconductor responds adversely to such changes.
And further objects of this invention include the techniques for the production of the wire that is to be used as the superconducting sensor conductor.